Sometimes I can't access the disk, the Dashboard stop in a blank page.
Sometimes I can access the Dashboard, but I can't change some options like Create Users, Create Folders, etc.

And now I can't access the disk for the anyway. I try direct cable (port 1 and 2), direct crossover cable (port 1 and 2), direct in isolated switch, and nothing. Don't load the Dashboard page. Stop in a blank page.

4.19. Reset to Factory
If for any reason you wish to reset your LaCie product to its out-of-
the-box state, follow this procedure:
CAUTION: Resetting the product will erase all Dashboard data
such as users, groups, shares, and settings.
CAUTION: After resetting to default, all files will be moved to a
folder called Recovery in Share and so by default will be available
only to the administrator.

If you have the possibility to connect all disks (you could leave one disk, due to redundancy) together to a Linux PC (Any PC booted from a Linux Live CD or -USB stick should do), you can reassemble the array, and copy the data from it.

You can connect the disks using USB-SATA converters, or the PC's SATA or eSATA connectors. Or a combination of them.

I'm 99% sure the raid is software raid, so the assembling is not hard. Assuming that you have connected 4 disks to a Ubuntu system, the procedure is:
Open a terminal (command prompt)
First identify your data partitions:

You're looking for 4 partitions sdx2, about 1TB in size each. (the size is given in kB). I'll assume they are sdb2, sdc2, sdd2 and sde2.
Now install the software raid manager (internet connection needed):

Many thanks for helping me with D2N2. I bought new power adaptor and it is working straight then updated to latest firmware. Now I am about to receive 5big v2 nextweek and its a 5Tb reset to default, working order with latest firmware. I'd like to back up its firmware to forum. Would you mind instruct me of how by steps again I am new with Ubunto. Much appreciated.
G